Yes. Beckett, in the midst of a s***** season, decided to accept the Red Sox's offer at reasonable money at 3/30 with a 4th year as a club option. He took the guaranteed money even though he knew the risks involved (ie outperforming that salary level, which he did this season).
Now why, if the Sox were to acquire Santana (who is a better pitcher than Josh Beckett), and he makes more money than Josh Beckett, why would they have to restructure his deal for fear of as you say, "pissing him off"? He assumed the risk of signing a deal for less money because of the guaranteed years.